This invention relates to a printing apparatus used with cut paper sheets and, more particularly, to improvements in an automatic paper sheet loading mechanism for such a printing apparatus.
Recently, serial printers used with cut paper sheets are finding extensive application with personal computers and word processors, as well as with data communication system terminal printers. Automatic paper sheet loading is desired for such serial printers. In the prior art, two different types of automatic cut paper sheet loading mechanism are in practical use, one for loading a plurality of cut paper sheets one after another, and the other for loading only a single cut paper sheet. The former type of loading mechanism requires, in addition to an ordinary paper feeding mechanism consisting of a platen roller or the like and a control circuit therefor, a paper feeding mechanism for feeding cut paper sheets one after another to the platen roller, a paper bail bar drive mechanism for releasing a paper bail bar from the platen roller, and a control circuit for these mechanisms. Therefore, this type of loading mechanism is inevitably large in scale, and high in price. In the latter type of loading mechanism, a cut paper sheet is set on the hopper and the paper bail bar is manually released from the platen roller. Thus, the paper feeding mechanism, paper bail bar drive mechanism and control circuit therefor are unnecessary, so that a simple and low price construction can be realized. On the demerit side, however, a load switch has to be depressed every time a cut paper sheet is loaded. Therefore, the operation is rather cumbersome compared to the former type of loading mechanism. In addition, the latter type of loading mechanism does not have means for determining the presence or absence of paper on the hopper. Therefore, idle paper feeding in the absence of paper is liable to result. In addition, erroneous paper loading caused by overlap loading of paper is likely to result from turning on the load switch again subsequent to the loading of a cut paper sheet.